In one aspect, this invention relates to a method for detecting the adulteration of one liquid hydrocarbon fuel with another liquid hydrocarbon fuel. In another aspect, the invention relates to a method for analyzing a liquid hydrocarbon fuel for the presence of a marker dye.
Trademark misuse by the dealers of branded liquid hydrocarbon fuels such as gasoline is a problem for the major oil companies. Oil companies go to great expense to make sure their branded products meet stringent specifications regarding volatility and octane number, for example, as well as to provide them with effective additive packages containing detergents and the like. Consumers rely upon the trademarks to assure themselves that the product being purchased is of high quality.
Unscrupulous gasoline dealers can make large profits by selling inferior product at the price consumers are willing to pay for a high quality branded product. Large profits can also be made by unscrupulous dealers simply by diluting the branded product with an inferior product. Policing dealers who blend branded products with inferior products is very difficult in the case of gasoline because the blended products will qualitatively display the presence of each component in the branded products. The key ingredients of the branded products are generally present in such low levels that quantitative analysis to detect dilution with an inferior product is very difficult, time consuming and expensive.
Marker MP dye is a commercial product produced by Morton Chemical which can be added to liquid hydrocarbon fuels such as gasoline and used as a tracer to detect trademark violations. When added in very low amounts it is non-visible and cannot be detected by other than chemical means. It can, however, be quantified by chemical analysis to determine the degree of adulteration with non-dyed product. To detect trademark violations Morton recommends a treat level of 20 parts per million (ppm). Methodology and reagents for quantifying Marker MP dye at these treat levels are also provided by Morton. Marker MP dye is quite expensive at $36/gal. At the 20 ppm level this results in a 0.075 cent/gal. treat cost which is prohibitively expensive for many programs. Marker MP dye has also been sold in foreign countries to detect tax evasion. To detect tax evasion the dye is added to the lower taxed product and qualitatively tested for in the higher taxed product.
The recommended Morton methodology for quantification involves the extraction of the dye from the gasoline with an acidic liquid extractant using a liquid/liquid extraction technique, followed by a color forming reaction. The intensity of the color can be measured after a timed interval in a colorimeter and related to concentration. The procedure is limited in sensitivity, is time dependent, is cumbersome to perform, is subject to analyst technique variances and interferences, and is limited in sample throughput. Sample throughput is a critical parameter for large scale screening tests. The safety considerations involved in shaking gasoline with an acid extractant are also of concern. Time consuming cleanup of the extraction flasks also limits sample throughput.